Cyclopentadienyl Ligand

Published on Web 01/15/2004

An Unprecedented Hybrid Scorpionate/Cyclopentadienyl Ligand Antonio Otero,*,† Juan Ferna´ ndez-Baeza,*,† Antonio Antin˜olo,† Juan Tejeda,† Agustı´n Lara-Sa´ nchez,† Luis Sa´ nchez-Barba,† Ana M. Rodrı´guez,† and Miguel A. Maestro‡ Departamento de Quı´mica Inorga´ nica, Orga´ nica y Bioquı´mica, UniVersidad de Castilla-La Mancha, 13071 Ciudad Real, Spain, and SerVicios Xerais de Apoio a´ InVestigacio´ n, Edificio SCI, Campus de ElVin˜ a, UniVersidade da Corun˜ a, 15071 A Corun˜ a, Spain Received October 21, 2003; E-mail: [email protected]

Metal complexes with donor-functionalized cyclopentadienyl ligands have been studied intensively in recent years because of their potential applications as catalysts in polymerization processes.1 Replacement of cyclopentadienyl ring hydrogens by various substituents has been shown to result in significant changes in both steric and electronic effects on the metal centers.2 The most recent strategy in the design and modification of catalysts for olefin polymerization involved the development of noncyclopentadienyl-based complexes of group 4 metals, with particular attention focused on nitrogen- and/or oxygen-containing ligands.3 Given the impact of ligand design, we recently reported4 the preparation of new “heteroscorpionate” ligands.5 Our new ligands are related to the tris(pyrazol-1-yl)methane system,6 but in this case one of the pyrazole groups is replaced by a carboxylate, dithiocarboxylate, or ethoxy group to give a small degree of steric hindrance and considerable coordinative flexibility. However, despite the development of donor-functionalized cyclopentadienyl ligands and the emerging importance of the “heteroscorpionate” ligands, hybrid scorpionate/cyclopentadienyllithium compound precursors for the introduction of these ligands into transition metal complexes are unknown. With the aim of addressing this situation, we have developed a simple and efficient synthetic route that allowed us to isolate the first hybrid scorpionate/ cyclopentadienyllithium compound as a precursor for a new class of tridentate ligand. Deprotonation at the methylene group of bis(3,5-dimethylpyrazol-1-yl)methane (bdmpzm)7 with BunLi, followed by reaction with 6,6-diphenylfulvene yielded the lithium compound [Li(bpzcp)(THF)] 1 [bpzcp ) 2,2-bis(3,5-dimethylpyrazol-1-yl)1,1-diphenylethylcyclopentadienyl] (see Scheme 1). Scheme 1. Summary of Reactions Leading to Compounds 1 and 2

The 1H and 13C{H} NMR spectra exhibits only one set of resonances, as would be expected for the presence of two equivalent pyrazolyl rings in the molecule. The mass spectrum (FAB) of 1 † ‡

Universidad de Castilla-La Mancha. Universidade da Corun˜a.

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Figure 1. ORTEP diagram of 1 with 30% probability ellipsoids. Selected bond lengths (Å) and angles (deg): Li(1)-O(1), 1.96(1); Li(1)-N(1), 2.37(1); Li(1)-N(3), 2.13(1); O(1)-Li(1)-N(3), 105.4(5); N(1)-Li(1)N(3), 83.4(4); O(1)-Li(1)-N(1), 103.5(5).

indicates a mononuclear formulation, which was corroborated by an X-ray crystal structure determination for 1 (see Figure 1).8 The geometry around the Li atom can be described as a distorted tetrahedron with a “heteroscorpionate” ligand that acts in a tridentate fashion (two coordinated pyrazole rings and a cyclopentadinyl ring) and one molecule of THF. Both Li-N distances [2.37(1) and 2.13(1) Å] are in good agreement with others determined for lithium scorpionate or poly(pyrazolyl)methane complexes.4a,d,9 The C5H4 ring is unsymmetrically bonded to the Li atom, with Li-C bond lengths ranging from 2.25(1) to 2.44(1) Å, and these distances are in agreement with other functionalized cyclopentadienyllithium complexes.10 This lithium compound is a new class of tridentate ligand and has been used for the synthesis of a new zirconium complex. Thus, lithium compound 1 reacted at -70 °C, in a 1:1 molar ratio (Scheme 1) with [ZrCl4] in THF to give, after the appropriate workup, the complex [ZrCl3(bpzcp)] (2), which was isolated as a red solid. The 1H NMR spectrum of this complex exhibits one singlet for each of the H4, Me3, and Me5 pyrazole protons and two multiplets for the Hc and Hd cyclopentadienyl protons, indicating that the two pyrazolyl rings are equivalent and that a symmetry plane exists. These results are consistent with an octahedral structural disposition, and κ3-NNη5Cp coordination for the bpzcp ligand is proposed. The 13C{H} NMR spectrum of complex 2 confirms this disposition. This complex constitutes the first example of a group 4 metal complex bearing a hybrid scorpionate/cyclopentadienyl ligand. To confirm the proposed structure for this complex, an X-ray crystal structure analysis was carried out (see Figure 2).8 The structure consists of a heteroscorpionate ligand bonded to the zirconium atom through the two nitrogen atoms and the cyclopentadienyl ring. In addition, the zirconium center is coordinated to three chlorine atoms. This center has a distorted octahedral 10.1021/ja0391558 CCC: $27.50 © 2004 American Chemical Society

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Figure 2. ORTEP diagram of 2 with 30% probability ellipsoids. Selected bond lengths (Å) and angles (deg): Zr(1)-N(3), 2.391(4); Zr(1)-N(1), 2.424(4); Zr(1)-Cl(1), 2.479(1); Zr(1)-Cl(3), 2.468(1); Zr(1)-Cl(2), 2.513(1); N(3)-Zr(1)-Cl(3), 160.66(9); N(1)-Zr(1)-Cl(1), 158.32(9); Cl(2)-Zr(1)-C(1), 148.6(1).

environment with a major distortion in the N(1)-Zr(1)-Cl(1) angle, which has a value of 158.32(9)°. The Zr(1)-Cl(1), Zr(1)-Cl(2), and Zr(1)-Cl(3) bond distances of 2.479(1), 2.513(1), and 2.468(1) Å, respectively, are as one would expect for a Zr pyrazolyl complex.11 In this complex, in contrast to lithium complex 1, the C5H4 ring is symmetrically bonded to the Zr atom with Zr-C bond distances of 2.523(4) to 2.572(4) Å. In conclusion, we describe here a simple and efficient method for the preparation of the first hybrid scorpionate/cyclopentadienyllithium compound as a new class of tridentate ligand. This compound is an excellent reagent for the introduction of this ligand into transition metal complexes, a fact confirmed by reaction with a zirconium halide. Acknowledgment. We gratefully acknowledge financial support from the Direccio´n General de Ensen˜anza Superior e Investigacio´n Cientı´fica, Spain (Grant No. BQU2002-04638-CO2-02). Supporting Information Available: Spectroscopic data and details of data collection, refinement, atom coordinates, anisotropic displacement parameters, and bond lengths and angles for complexes 1 and 2. This material is available free of charge via the Internet at http:// pubs.acs.org. References (1) See for example: (a) Deng, D.; Qian, C.; Wu, G.; Zheng, P. J. Chem. Soc., Chem. Commun. 1990, 880. (b) Qian, C.; Wang, B.; Wu, G.; Zheng, P. J. J. Organomet. Chem. 1992, 427, C29. (c) Anwander, R.; Hermann, W. A.; Scherer, W.; Munck, F. C. J. Organomet. Chem. 1993, 462, 163. (d) Molander, G.; Schumann, H.; Rosenthal, E. C. E.; Demtschuk, J. Organometallics 1996, 15, 3817. (e) Schumann, H.; Rosenthal, E. C. E.; Demtschuk, J. Organometallics 1998, 17, 5324.

(2) (a) McKnight, A. L.; Waymouth, R. M. Chem. ReV. 1998, 98, 2587. (b) Siemling, U. Chem. ReV. 2000, 100, 1495. (c) Butenscho¨n, H. Chem. ReV. 2000, 100, 1527. (3) See, for example: (a) Scollard, J. D.; McConville, D. H. J. Am. Chem. Soc. 1996, 118, 10008. (b) Scollard, J. D.; McConville, D. H.; Vittal, J. J. Organometallics 1997, 16, 4415. (c) Fokken, S.; Spaniol, T. P.; Okuda, J.; Serentz, F. G.; Mullhaupt, R. Organometallics 1997, 16, 4240. (d) Gibson, V. C.; Kimberely, B. S.; White, A. J. R.; Williams, D. J.; Houd, P. Chem. Commun. 1998, 313. (e) Warren, T. H.; Schrock, R. R.; Davis, W. M. Organometallics 1998, 17, 308. (4) (a) Otero, A.; Ferna´ndez-Baeza, J.; Tejeda, J.; Antin˜olo, A.; CarrilloHermosilla, F.; Diez-Barra, E.; Lara-Sa´nchez, A.; Ferna´ndez-Lo´pez, M.; Lanfranchi, M.; Pellinghelli, M. A. J. Chem. Soc., Dalton Trans. 1999, 3537. (b) Otero, A.; Ferna´ndez-Baeza, J.; Tejeda, J.; Antin˜olo, A.; CarrilloHermosilla, F.; Diez-Barra, E.; Lara-Sa´nchez, A.; Ferna´ndez-Lopez, M. J. Chem. Soc., Dalton Trans. 2000, 2367. (c) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Carrillo-Hermosilla, F.; Tejeda, J.; Dı´ez-Barra, E.; LaraSa´nchez, A.; Sa´nchez-Barba, L.; Lo´pez-Solera, I.; Ribeiro, M. R.; Campos, J. M. Organometallics 2001, 20, 2428. (d) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Carrillo-Hermosilla, F.; Tejeda, J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Rodrı´guez A. M.; Lo´pez-Solera, I. Inorg. Chem. 2002, 41, 5193. (e) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Expo´sito, M. T.; Rodrı´guez A. M. J. Chem. Soc., Dalton Trans. 2003, 1614. (5) (a) Trofimenko, S. Scorpionates. The Coordination Chemistry of Polypyrazolylborate Ligands; Imperial College Press: London, 1999. (b) Higgs, T. C.; Carrano, C. J. Inorg. Chem. 1997, 36, 291. (c) Higgs, T. C.; Ji, D.; Czernuszewicz, R. S.; Matzanke, B. F.; Schunemann, V.; Trautwein, A. X.; Helliwell, M.; Ramirez, W.; Carrano, C. J. Inorg. Chem. 1998, 37, 2383. (d) Hammes, B. S.; Carrano, C. J. Inorg. Chem. 1999, 38, 3562. (e) Hammes, B. S.; Carrano, C. J. J. Chem. Soc., Dalton Trans. 2000, 3304. (f) Ghosh, P.; Parkin, G. J. Chem. Commun. 1998, 413. (g) Ge, P.; Haggerty, B. S.; Rheingold, A. L.; Riordan, C. G. J. Am. Chem. Soc. 1994, 116, 8406. (h) Stibrany, R. T.; Knapp, S.; Potenza, J. A.; Schugar, H. J. Inorg. Chem. 1999, 38, 132. (i) Lopes, I.; Lin, G. Y.; Domingos, A. McDonald, R.; Marques, N.; Takats, J. J. Am. Chem. Soc. 1999, 121, 8110. (j) Lo´pez-Herna´ndez, A.; Mu¨ller, R.; Kopf H.; Burzlaff, N. Eur. J. Inorg. Chem. 2002, 671. (6) (a) Ferna´ndez-Baeza, J.; Jalo´n, F. A.; Otero, A.; Rodrigo, M. E. J. Chem. Soc., Dalton Trans. 1995, 1015. (b) Antin˜olo, A.; Carrillo-Hermosilla, F.; Diez-Barra, E.; Ferna´ndez-Baeza, J.; Ferna´ndez-Lopez, M.; LaraSa´nchez, A.; Moreno, A.; Otero, A.; Rodrı´guez, A. M.; Tejeda, J. J. Chem. Soc., Dalton Trans. 1998, 3737. (7) (a) Sebastian, J.; Sala, P.; Del Mazo, J.; Sancho, M.; Ochoa, C.; Elguero, J.; Fayet J. P.; Vertut, M. C. J. Heterocycl. Chem. 1982, 19, 1141. (b) Dı´ez-Barra, E.; de la Hoz, A.; Sa´nchez-Migallon, A.; Tejeda, J. J. Chem. Soc., Perkin Trans. 1 1993, 1079. (8) Crystallographic data for 1: C33H37LiN4O, monoclinic, P21/a, a ) 16.576 (3), b ) 11.509 (4), c ) 17.059 (2) Å; β ) 115.36(2)°; V ) 2941 (1) Å3; Z ) 4; Dcalcd ) 1.131 g/cm3; λ(Mo KR) ) 0.71073 Å; µ(Mo KR) ) 0.69 cm-1; 250(2) K; NONIUS-MACH3 diffractometer, graphite monochromator; 5290 unique reflections; R ) 0.0746; Rw ) 0.1423. Crystallographic data for 2: C29H29Cl3N4Zr‚2THF, monoclinic, P21/n, a ) 12.2220(11), b ) 23.628 (2), c ) 12.8891 (12) Å; β ) 100.935(2)°; V ) 3654.6 (6) Å3; Z ) 4; Dcalcd ) 1.409 g/cm3; λ(Mo KR) ) 0.71073 Å; µ(Mo KR) ) 5.56 cm-1; 173 (2) K.; BRUKER SMART CCD diffractometer, graphite monochromator; 7472 unique reflections; R ) 0.0538; Rw ) 0.1530. Complete details of the data collection and refinement of 1 and 2 are included in Supporting Information. (9) Reger, D. L.; Collins, J. E.; Matthews, M. A.; Rheingold, A. L.; LiableSands, L. M.; Guzei, I. A. Inorg. Chem. 1997, 36, 6266. (10) (a) Qian, B.; Henling, L. M.; Peters, J. C. Organometallics 2000, 19, 2805. (b) Culp, R. D.; Cowley, A. H. Organometallics 1996, 15, 5380. (11) Oshiki, T.; Mashima, K.; Kawamura, S.; Tani, K.; Kitaura, K. Bull. Chem. Soc. Jpn. 2000, 73, 1735.

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